Process of manufacturing switch contacts



May 24, 1960 A. P. SWIFT 2,937,434

PROCESS OF MANUFACTURING SWITCH CONTACTS Filed June 14, 1956 INVENTOR,

ATTORNEYS.

United States Patent() PROCESS OF MANUFACTURING SWITCH CONTACTS Arthur P. Swift, Woodland Hills, Calif., assignor to General Controls (10., Glendale, Calif., a corporation of California Filed June 14, 1956, Ser. No. 591,338

1 Claim. (Cl. 29155.55)

This invention relates to contacts for electrical circuit controllers; more particularly, it relates to the attachment of a contact member in an arm by cold-forming operations often referred to as staking" operations. The contact member may be in the form of a plate or disk that is made from expensive material, such as silver or platinum, to provide an efficient contact area. There is thus an attendant economy since the supporting arm may be made from relatively inexpensive material, while the actual contacting member of expensive material may be of limited area.

It is one of the objects of this invention to provide a contact member of this character by the aid of simple inexpensive machine operations.

It is another object of this invention to provide a durable contact structure in which the contacting element is firmly held in place by the arm, and by the aid of inexpensive construction.

This invention possesses many other advantages, and has other objects which may be made more clearly apparent from a consideration of several embodiments of the invention For this purpose, there are shown a few forms in the drawings accompanying and forming part of the present specification. These forms will now be described in detail, illustrating the general principles of the invention; but it is to be understood that this detailed description is not to be taken in a limiting sense, since the scope of the invention is best defined by the appended claims.

Referring to the drawings:

Figure 1 is a top plan view, illustrating the first step of the process of manufacturing the switch contact arm;

Fig. 2 is a longitudinal sectional view thereof, and includes an illustration of the final forming operation performed on the arm;

Figs. 3 and 4 are sectional views illustrating two successive steps required to secure the inlaid contact piece to the arm, the sections corresponding to a plane designated by line X-X of Fig. 2;

Fig. 5 shows a portion of a strip adapted to be advanced step-by-step with respect to a progressive die or punch, and illustrating the progressive steps in the punching and forming operations; and

Fig. 6 is a fragmentary enlarged sectional view through the inlay, illustrating the completed device.

A switch arm 1 is shown which may be made of metal, such as copper or brass, to provide good conductivity. The arm is intended to be attached to an operating mechanism by the aid of an aperture 2. As shown in Fig. 2, the arm 1 may be bent to conform it to its desired use,

the final forming being accomplished in the manner indicated by the phantom lines 3, corresponding to the flat shape, which is bent to conform to the form shown in full lines.

The inlay 4, shown in completed form in Fig. 6, is made of good conducting material, such as silver or platinum. Since such material is relatively expensive, the provision of an inlay of this character in an inexpen- Patented May 24, 1960 1 sive metal arm 1 renders it possible to provide an inexpensive structure. Silver and platinum have highly desirable properties for switch contacts, as is now well understood.

The first step in fastening the inlay 4 in position is indicated in Figs. 1 and 2. Thus the inlay 4 is preferably in the form of a circular disk which has a clearance of a few thousandths of an inch in an aperture or recess 5 provided in the arm 1. For example, if the disk inlay 4 is .234 inch in diameter, the aperture 5 may have a diameter of .236 inch. The clearance is-shown greatly exaggerated in Figs. 1 and 2. The disk inlay 4 and the arm 1 are preferably of the same thickness. In the present instance, it may be .04 inch thick.

The first staking operation illustrated in Fig. 3 is for the purpose of deforming the edge of the disk inlay 4 so that the overall diameter of the inlay is enlarged by a flange, to be firmly placed into engagement with the wall of aperture 5. This is accomplished by the aid of a lower punch 6 and an upper punch 7. The lower punch 6 is provided with an annular rib 8 having an outer peripheral surface fitting into the lower portion of the aperture 5. The inner periphery is spaced inwardly of the edge of the disk. The upper punch 7 is provided with a corresponding annular rib 9.

The disk 4 is placed on top of the rib 8, and then the die or upper punch 7 is lowered in axial alignment with the punch 6 so as to perform a staking operation. This staking operation upsets the peripheral portion of the inlay 4 to form a flange 10. This upsetting or deforming operation reduces the thickness of the inlay 4 adjacent the edge and defines a thin edge portion or flange 10. Due to this reduction in thickness, the flange 10 has an external diameter greater than the original diameter of disk 4. By this expansion, the thinned edge or flange 10 comes into firm contact with the inner surface or wall of the aperture 5.

The last staking operation is illustrated in Fig. 4. In this figure, the upper and lower edges of the aperture 5 are deformed and turned or folded over to overlie the thinned edge or flange 10. This is illustrated by the overlying portions 11 and 12 of the aperture.

In order to accomplish this result, use is made of a lower punch 13 and an upper punch 14. Each of these punches is formed respectively with projections 15 and 16 producing an indentation around the edge of the aperture 5; for deflecting or bending or folding the metal around the aperture 5 over the flange or rib portion 10 of the insert 4. The projections 15 and 16 are relatively narrow at their engaging surfaces, but are widened at the base by the aid of a curve to provide appropriate rounded surfaces 17 for the bent-over portions 11 and 12. The final form of a completed article, together with the rounded surfaces 1.7 is shown most clearly in Fig. 6.

By this means the inlay 4 is held firmly in place in the arm 1 and in good electrical contact therewith.

The successive staking operations as above described can be performed by aid of a progressive die or punch. Thus in Fig. 5 a strip of metal 18 is shown which is progressively advanced, first of all to produce the apertures 2 and 5. The first staking operation results in the formation of the narrow flange or rib 10. At the second station, the overlying portions 11 of the aperture 5 are indicated. At the same time, the arm 1 may be cut away from the strip as indicated by the phantom lines 19.

The inventor claims:

The process of attaching a flat metal contact inlay into a clearance aperture in a flat metal member, the thicknesses of both the member and the inlay being substantially equal, so that the opposite surfaces of the inlay are respectively substantiallyocoplanar with the opposite surfaces of the metal member, which comprises: placing the inlay into the clearance aperture; exerting a compressive force on opposite sides of the inlay and only at the peripheral portion thereof, to cause a thinningof the 5 inlay edge and an expansion of the edge into firm contact With the Wall of the apertureythe thinned edge there by being intermediate the opposite surfaces of the inlay; and then folding the opposite edges of the aperture over the thinned edge and into contact therewith, by aid of 10 an indentation around the edge of the aperture.

1,105,399 Cadell July 28, 1914 15 Rosenfeld July 11, Haas Nov. 29, Larson Oct. 10, Van Inwagen Apr. 17, Weisberg Dec. 14, Flurnerfelt Nov. 18, Enzler July 28, High Aug. 9, Foulds et a1. Oct. 30, Frank et al Sept. 30,

FOREIGN PATENTS France Oct. 21, France May 17, 

